The major issue when it comes to a webcast is your internet connection. Do you have a reliable upload speed? A broadband speed test will help you establish that and the quality of that connection will determine the type of picture you can send to the web. If you are in a conference centre its worth remembering that when your event is taking place delegates may also be using this connection so it’s worth looking into how you can ringfence that speed for your own webcast. (Chat to the IT guy!)